1. Field of the Invention
The present invention relates to an organic EL (electro luminescence) device and an organic EL (electro luminescence) display apparatus employing this organic EL device. In this specification, the technical term ‘electro luminescence’ is abbreviated to EL. In addition, two sides of a component are referred to as respectively particular and other sides of the component. By the same token, two electrodes of a component are referred to as respectively particular and other electrodes of the component. In the same way, two faces of an area are referred to as respectively particular and other faces of the area.
2. Description of the Related Art
In an organic EL display apparatus employing an organic EL device including an organic EL light emitting element, the luminance of the organic EL device is controlled by a current flowing through the organic EL device. Strictly speaking, the luminance of the organic EL device is the luminance of the organic EL light emitting element employed in the organic EL device. In addition, much like a liquid-crystal display apparatus, a simple matrix method and an active matrix method are each generally known as a driving method of the organic EL display apparatus. In comparison with the simple matrix method, the active matrix method has a shortcoming of a complicated structure. Nevertheless, the active matrix method offers merits such as a high degree of image luminance.
A circuit for included in the organic EL device as a circuit for driving an organic EL light emitting element employed in the organic EL device is, for example, a driving circuit having five transistors and one capacitor. In the following description, the driving circuit employing five transistors and one capacitor is referred to as a 5Tr/1C driving circuit. The 5Tr/1C driving circuit is described in documents such as Japanese Patent Laid-open No. 2006-215213. As shown in FIG. 36, the 5Tr/1C driving circuit employs five transistors and a capacitor C1. The five transistors are a video-signal write transistor TSig, an element driving transistor TDrv, a light-emission control transistor TEL—C, a first-node initialization transistor TND1 and a second-node initialization transistor TND2. In this configuration, the other source/drain area of the element driving transistor TDrv forms a second node ND2 whereas the gate electrode of the element driving transistor TDrv forms a first node ND1. In the following description, the other source/drain area of the element driving transistor TDrv is a source/drain area provided on a side close to the organic EL light emitting element to serve as the other source/drain area of the element driving transistor TDrv.
Each of the transistors cited above is, for example, a TFT (Thin Film Transistor) of an n-channel type. The organic EL light emitting element denoted by notation ELP in figures in this specification is provided on a created inter-layer insulation layer for example, so as to cover the driving circuit. The anode electrode of the organic EL light emitting element ELP is connected to the other source/drain area of the element driving transistor TDrv. On the other hand, a voltage VCat of 0 volts, for example, is applied to the cathode electrode of the organic EL light emitting element ELP. Notation CEL shown in each figure of this specification denotes the parasitic capacitance of the organic EL light emitting element ELP.